What is Dystonia?
This site is maintained by the Dystonia Brazilian Association and focus on some basic facts about clinical aspects and research on the various forms of Dystonias. It is intended to provide an on-line guide for patients and their families.
Last updated : March 22, 2004
The term Dystonia is used to describe a group of diseases whose main feature is the presence of involuntary muscle spasms producing movements and/or abnormal postures. These muscle spasms may affect a discrete muscle group such as the eyelid, neck or hand muscles (focal dystonias), two or more contiguous regions(segmentar dystonias), one side of the body (hemidystonias) or multiple regions (generalized dystonias).
In most patients a cause cannot be identified. It is believed that dystonic abnormal movements result from a dysfunction within a brain region known as the basal ganglia. In certain circumstances, in which the basal ganglia are not functioning properly, some muscle groups contract in an excessive manner producing dystonic movements and postures.
In focal forms there is involvement of a limited body part. In most patients, onset of symptoms occurs in the adult after the third or fourth decade of life. The first manifestations are mild and can be noticed only during specific motor acts such as speaking, writing, reading or walking. After some time, involuntary muscle contractions become more intense and appear even at rest. Some patients may present with pain in the abnormally contracting muscles. Even though symptoms tend to remain focal, there can be spreading to contiguous muscles as well.
The most common types of focal dystonias are named according to the involved body part such as:
In blepharospasm there is involvement of the muscles surrounding the orbits which are responsible for closing the eyelids. The initial symptoms are increased frequency of blinking, irritable eyes and increased sensitivity to light. As the disease progresses, blinking become more frequent and severe and difficulty in maintaining the eyes opened may take place. Stress and exposure to intense light tend to worsen symptoms and for this reason some patients may be relieved by wearing sunglasses.
This type is characterized by muscle spasms localized to the inferior parts of the face such as the lips, tongue, mouth and mandibular area. There can be difficulty to open or close the mouth, swallowing and articulating words all of which are a frequent source to the social embarassment experienced by many patients.
This is the most common type of focal dystonia. One or several muscles surrounding the neck are involved on one or both sides. Thus, the head and neck can present with a variety of abnormal postures (rotation, lateral deviation, flexion, extension or a combination of these). Oscillations in the severity of symptoms are common. Worsening by stress and fatigue and improvement with rest or when lying in the horizontal position are the rule.
This is a focal dystonia in which there is involvement of the vocal folds and sometimes of the larynx, pharynx and other facial muscles. Depending on the type of muscle contraction the voice may acquire a strangle or a whispered quality.
When an arm is affected by dystonia, in the begining it may only manifest itself during specific motor acts such as writing, typing or playing an instrument. In this initial phase, these dystonias are known as occupational cramps. The most common occupational cramp is Writer's cramp which occurs only during writing and remains limited to that arm. After some time, however, muscle spasms may occur also during other motor acts or even at rest. To the present it is not known why the persistent use of a muscle group would predispose some people to develop dystonia but some as yet undetermined dysfunction of the basal ganglia may play a role in its development.
In segmentar dystonias, various contiguous muscle groups are affected. The most common form is cranial dystonia which is a combination of blepharospasm and oromandibular dystonia. Sometimes there is involvement of the tongue, larynx, pharynx, vocal cords and neck muscles as well.
Other types of segmentar dystonias include braquial (involving one or both arms), crural(legs) and axial dystonia (trunk and/or neck)
Hemidystonias may begin at any age and typically there is involvement of one side of the body. They are less common than focal or segmentar dystonias and are usually related to an identifiable structural lesion situated in the contralateral basal ganglia.
These are rare forms of dystonia. The first symptoms occur during childhood or adolescence, usually in one or both feet. They may be first noticed during walking but later may appear even at rest. As the disease progress, other muscles become involved and severe disability may ensue. In more advanced cases, patients may be unable to walk and may need assistance for routine daily activities. Generalized dystonias may be sporadic (when there is no other affected member in the family) or hereditary (when there are other members affected in the same family).
Treatment of Dystonias
The ideal treatment should be one that could remove its cause. However, despite recent advances in research and in the development of new diagnostic tools, in the majority of patients no cause can be identified. Thus, current approach to treatment focus mainly on measures aimed at reducing excessive muscle contraction (i.e.symptomatic treatment).
There are three types of symptomatic treatment:
Pharmacologic treatment
Pharmacologic treatment means treatment with medicines (administered either orally or parenterally) which exert a systemic effect i.e.they are distributed to the whole body. In order to be effective against dystonia, drugs must have specific properties capable of reducing abnormal muscle contractions. These drugs include muscle relaxants and some agents acting upon basal ganglia neurotransmitters. They are often effective in several forms of generalized dystonias but have only limited effect on focal and segmentar dystonias of the adult.
Botulinum toxin
Botulinum toxin is a substance produced by the bacteria Clostridium botulinum and have the property of interfering in the process of muscle contraction. Its usefulness in medical practice has been widely recognized and it is administered through intramuscular injections of small amounts directly in the involved muscles. Its action is exclusively local and there is no significant systemic effects. This is the most effective therapeutic method for focal and segmentar dystonias and side effects are only mild and transient.
The therapeutic action of botulinum toxin begin a few days after the injection and its effect lasts for an average of three months. Thus, periodic injections at 3-6 month intervals are reccomended in order to achieve persistent control of symptoms.
Surgical treatment
This is restricted to specific cases, most often those with poor response to medications or botulinum toxin. The myectomy consists in the surgical removal of part of the muscles surrounding the eyelids and is effective in cases of blepharospasm. Some cases of torticollis may benefit from cervical ryzotomy in which selected cervical roots innervating the abnormally contracting muscles are cut. Patients with limb dystonias or the generalized form may improve with thalamotomy which consists in a surgical lesion of the thalamus
About the Association The The Dystonia Brazilian Association is a non-profit organization whose main goals are to increase public and medical awareness of dystonia and to provide support for patients and their families.
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GlossaryDystonia - Syndrome characterized by sustained muscular contractions, causing repetitive or twisting movements, or abnormal postures.
Neurotransmitters - Chemical substances responsible for the communication between nerve cells. Some neurotransmitters are: dopamine, acetylcholine, serotonin, norepinephrine and gama-aminobutyric acid.
Basal Ganglia - Nuclear masses located deep in the brain and related to important functions in motor control. The main structures constituting the basal ganglia are: corpus striatum (striatum and globus pallidus), substantia nigra, and subthalamic nucleus. Disturbances in various parts of the circuit linking these structures may give rise to diseases such as Parkinson’s disease, Huntington’s disease and Dystonias, among others.
Thalamus - Major nucleus located deep in the brain. It receives informations from the basal ganglia and send its projection to the cerebral cortex. Discrete surgical lesions in the thalamus, the thalamotomies, may improve some symptoms arising from disturbances in the basal ganglia.
Botulinum toxin - Neurotoxin produced by the bacteria Clostridium botulinum. This is an excellent example of how a toxic substance may function as a therapeutic agent if administered in small and controlled doses. Given its blocking action at the neuromuscular junction, it has been used in several conditions dominated by excessive muscular contractions. Among these conditions are: dystonias, spasticity, motor tics and certain types of tremors.
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